The only thing more impressive than The Killing Fields itself, is one of the stars central to the film - Haing S Ngor, a real-life doctor and survivor of the Cambodian genocide that Joffe's film focuses upon. His performance adds a grace note of repectful authenticity to a tough and distressing film of one of the bloodiest periods of the 20th century.

Cambodia at the beginning of the 1970s is not a pleasant place to be. The Vietnam War has spilled over its borders and the country is now in a state of chaos, as Pol Pot's Khymer Rouge rebels have risen up against the government and unleashed a genocidial purge in an attempt to take the country back to an agricultural "Year Zero" to essentially restart civilisation. The US army is both blind and deaf to the situation, concerned only with getting its citizens, both military and civilian, the hell out of there. That includes journalist Sid Schemberg (Sam Waterston), his photographer, Al (John Malkovich) and their local guide and native journalist, Dith Pran (Haing S Ngor); a task only made more difficult and dangerous by the brutal forces tearing the country apart.

Joffe directs this horror with a sad-eyed and unflinching gaze. He never dips into sentimentality or an exploitative rush to see as much blood as possible, instead keeping the savagery on the borders, just out of sight of everyone, while casually littering the film with horrific, disturbing details. The blood-spattered walls of a hospital, the background sight of corpses left to rot in the street, the random bombings devastating the streets and towns of Cambodia, all serve to create a true vision of hell on earth, a place where all pretence at order and civilisation has all but disappeared.

It creates an unsettling and dread-ridden atmosphere within the film of a bad situation that is only getting to get much, much worse on an inconceivable level. Joffe winds the tension up subtly, catching us off-guard with sudden developments such as an evacuation that's going to happen immediately - apart from all Cambodian natives, thus leaving Pran with an impossible choice to make. We don't see it coming and are thus as blind-sided and desperate as Sid and Al to not only get their hides out of the country alive, but their friend's, too. Joffe blends the small details of survival with the reality of history superbly, making the simple development of a passport photo an event filled with nail-biting tension.

It's a world of cruelty envisaged here, and when the film's final third takes a turn into survivalist drama, it kicks up another level into something beyond wholly and horribly engrossing into something emotionally tough and brutal. Yet what keeps you watching are the performances, keeping a human core to this history lesson throughout. Waterston is both intense and understated at the same time, full of wiry selfishness at first, only concerned with getting the scoop on the massacre before everyone else. His eventual turn from this into guilt and righteous indignation is powerful, because, like the rest of the film, Joffe never over-eggs it. It's simply a reaction to events and Joffe wisely recognises the inherent power of it. Malkovich is also good, but it is Ngor, in an Oscar-winning performance, who deservedly walks away with the film. As an amateur, you can tell the scenes he's least comfortable with, mainly when he has to deliver exposition. But as a survivor of these events, that's not what he's there for. His performance simply aches with sadness and rage and fear; one glance from his tired and experienced eyes telling you more about this country and its people than any other actor with reams of dialogue could. It goes beyond emotional honesty - his performance IS the film and IS this period in history.

Joffe mainly keeps the lid firmly buttoned down on sentimentality throughout. The two times he allows himself an indulgence is Sid numbly and silently watching a TV report on the on-going massacre, the camera focused upon his eyes, filled with a whole range of emotions; and the second is the justly-remembered ending. And both these times are as devastating as the rest of the film.